Containers of this type have--as is customary with canisters--a very definite volume. Moreover, they also have a very definite shape which is for the most part flat rectangular. They are produced either from sheet metal in the form of deep-drawn parts or by injection molding or blow molding or by centrifugal casting, etc.
The conventional containers have the following shortcomings:
(a) Even sheet metal canisters have transition radii between the side walls and the bottom wall. The transition radius--which in the case of containers made of plastics is still larger, particularly when they are produced by blow molding or by centrifugal casting--gives away part of the volume which is no longer available to the container. This gets the designer into difficulties since the gross volume occupied by the container and any handles and pouring spouts which may be present should be as close as possible to the net volume. PA1 (b) When, for example, a 5-1 canister or a 10-1 canister falls over, only relatively small masses are moved in that case. When, however, a 20-1 or a 30-1 canister falls over, the consequences may be serious. These containers have a considerable height, a width not quite as large and a very much smaller depth. When they fall over, they fall on their sides because they are least stable in this direction. This falling over is facilitated by the aforementioned radii because they shift the region farthest on the outside by about 20% of the canister depth toward the inside, with the canister depth being the smallest dimension to begin with. PA1 (c) In the deep drawing of sheet metal but still more so in the blow molding of plastics, in centrifugal casting, etc., these radii are the places with the least material thickness. This is undesirable in many different respects: It is in the bottom region that the container is subject to the greatest wear and tear. But this is exactly the place where the material is thinnest. If the containers are used as gasoline canisters, certain minimum wall thicknesses must be maintained in order to safeguard the diffusion tightness of the container. Many testing regulations of various countries specify a minimum wall thickness. The way to live up to this specification is to overdimension the thickness of the other walls which results in the consumption of more material and also makes the container heavier.